Forsus on the Archwire
Drs. Miller, Tieu, and Flores-Mir's article titled "Incisor inclination changes produced by two compliance-free Class II correction protocols for the treatment of mild to moderate Class II malocclusions" is in the online version of the Angle Orthodontist. It is based on Dr. Bob Miller's clinical study.
He compared 36 Class II patients treated in one phase with Forsus to the archwire in a full edgewise appliance to 38 similar Class II patients treated in two phases with Xbow followed by a full edgewise appliance. The Forsus to the archwire group was finished in an average of 30.2 months. The Xbow group was finished in an average of 24.2 months, which includes a 4 to 6 month rest period to allow for relapse. The two phase Xbow patients were completed 6 months faster on average than the one phase Forsus to the archwire patients. The Forsus to the archwire group had full braces for an average of 26.75 months. The Xbow group had full braces for an average of 16.68 months, or 10 fewer months.There was no significant difference in the lower incisor to mandibular plane angle between the two groups. The Xbow patients ended up with lower incisors at an average of 100 degrees to mandibular plane which is considered a reasonable compromise for non-extraction Class II compensation.
Most clinicians who have mastered the Xbow rarely use Forsus on the archwire. The side-effects of Forsus on the archwire are especially problematic when the spring is used unilaterally late in treatment. The unilateral posterior openbite and anterior canting requires prolonged treatment with good elasitc cooperation to recover from. We do not see the anterior canting when the spring is used unilaterally on a Xbow and any side-effects such as posterior openbite or lower incisor proclination relapse before phase two. The fact that the first bicuspids are already Class I after Xbow therapy reduces the time in phase two braces and the need for side-effect correction with elastics.
Unilateral posterior openbite and occlusal cant after unilateral Class II spring on the archwire. This side effect requires good elastic compliance to resolve. The cant does not always completely level. This side effect occurs late in treatment when you should be fine tuning before deband.
In most moderate to severe non-extraction or borderline extraction Class II cases I use a two phase approach with the Xbow. With the borderline extraction cases if the case becomes too protrusive in phase two we then extract. In an extraction case we begin with headgear and start Class II elastics as soon as rectangular stainless steel arch wires are placed and space closure is begun. In deep bite cases we add a bite turbo as soon as there is incisor contact. Once the lower spaces are closed we decide whether to finish with headgear and elastics or place Forsus. The reason I use headgear and elastics is twofold. First, I don't like to wait to begin Class II mechanics until I have placed rectangular stainless steel arch wires. You may be missing out on growth, especially in late eruption or early maturing females. Second, in a deep bite case you want the lower posterior eruption that elastics give. Forsus intrudes upper molars temporarily.
I use the same principles when using the Forsus device with a full edgewise appliance as I do with Xbow. Use the 22mm Direct Pushrod distal to the lower first bicuspid instead of the canine, if possible. This keeps the Forsus device more compact and moves it distal to the anterior curvature of the arch, preventing the need for rod adjustments. It also keeps the spring distal to the Obicularis Oris muscle, preventing sores. The only difference is you cannot fully compress the spring with an edgewise appliance if you use a bracket as the anterior stop. If you do be prepared to rebond the bracket. Don't forget to steel tie the first bicuspids. Reactivate the springs with crimpable stops on the rods or use longer rods.
Dr. Bob Miller taught us to hook up the pushrod using an Alastic KX module to activate the spring but at the same time remove the force from the canine or first bicuspid bracket. This also negates the need to cinch the distal end of the arch wire. Place the springs and pushrods as you would normally but don't close the loop yet. Make the pushrod adjustments leaving 1mm of play in the spring, remove the pushrod, pre-stretch a KX-1 module, place the KX module on the pushrod and close the loop, remove the arch wire from the mouth and place the pushrods on the archwire, replace the arch wire with the pushrods (do not cinch the distal end of the arch wire), tie in the arch wire, hook the KX module to the first molar hook using floss and a floss threader over the second bicuspid bracket and down between the second bicuspid and first molar, then place the pushrod in the spring. This completely activates the spring without debonding the canine or first bicuspid bracket. If we place the 22 mm or 25 mm pushrod distal to the first bicuspid we use a KX-1 module. We also use a KX-1 module distal to the canine in a bicuspid extraction case.
Alastic KX-1 module placed with floss threader
Alastic KX-1 module and lingual tuck-in pushrod adjustment on 25mm rod
Alastic KX-1 module hook-up distal to canine (severe Class II, patient decided against mandibular advancement surgery after preparation)
Alastic KX-1 Module hook-up distal to first bicuspid
Alastic KX-1 Module hook-up distal to canine (bicuspid extraction) with a 22 mm pushrod.
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